Objectives: 

Aging is associated with an increase in motility gastrointestinal disorders. Among other experimental proposals, free radical theory of aging suggests that aging results from the accumulative damage of free radicals produced during cell respiration. The aim of our study was to investigate the effect of aging on the submucosal (Meissner) and myenteric (Auerbach) plexuses surfaces and also assess a marker of oxidative damage in these duodenal areas.

Materials: 

Specimens of duodenum were obtained from 3, 12 and 24 month old Wistar rats (n=4/group). Tissues were fixed in formaldehyed buffered solution. After dehydration in graded concentrations of ethanol, the fragments were embedded in paraffin, sectioned (thickness, 3 mm) and stained with hematoxilin-eosin and inmunohistochemical procedures. To measure Meissner and Auerbach plexuses we used a rabbit polyclonal anti-S-100 protein antibody. Results of these areas were expressed as percentage of the whole submucosal and myenteric layers, respectively. The nervous plexuses cells with exacerbated oxidative damage were marked using a mouse monoclonal anti-malondialdehyde (MDA) antibody. All morphometrical measurements were obtained using the Cell-D software. Statistical comparison were performed by a student's t-test with a level of significance of p<0.05.

Results: 

Meissner plexus area (%) showed not significant changes in 3, 12 and 24 month old rats (3: 2.5±0.2; 12: 2.35±0.12; 24: 2.23±0.2). Nevertheless, we obtained a severe decrease associated to aging in Auerbach area (%) (3: 3.25±0.33; 12: 2.83±0.34; 24: 1.97±0.16). Positive MDA cells (cel/mm²) increased in both nervous plexuses (Meissner: 3: 78.6±18.1; 12: 142.8±20.2; and 24: 153.1±21.5; Auerbach: 3: 15.3±3.9; 12: 30.4±6.3; 24: 41.4±1.8).

Conclusions: 

These findings are consistent with the idea that the accumulation of oxidative damage due to aging may be, at least, partially responsible of the reduction in the duodenal Meissner and Auerbach plexuses surfaces in old animals.